Car washes utilize auto conveyors having rollers carried by a chain each of which are selectively positioned to engage a tire of a vehicle to push the vehicle along the track and through the car wash.
In many widely used designs, a plurality of spaced roller assemblies are secured along the length of an endless conveyor chain, which chain extends below but along the path of travel of the auto.
Each roller assembly includes a set of outboard guide rollers which ride along an upper track and also an inboard set of pusher rollers which move against the auto tire when in the engaging position. The roller sets are each mounted on a roller support arm which extends downwardly through a slot in the track to the chain running below.
In U.S. Pat. Re No. 30,026, describing such a design, each of the guide rollers and pusher rollers are mounted on a common axis for independent rotation. The guide rollers are necessarily of larger diameter than the pusher rollers to support the pusher roller above the surface of the track and allow free rotation of the pusher rollers with rotation of the vehicle tire.
This approach has created problems when a conveyed auto is equipped with wide tires, which sometimes will engage one or both of the guide rollers, causing the guide rollers to be dragged along the track. This condition leads to greatly increase drag, as well as early wear out and failure of the rollers and/or the track. Another problem is encountered in that the smaller diameter pusher rollers sometimes slip beneath the tires so that the auto escapes its driving connection with the chain. These small diameter rollers are subject to early wearout due to the excessive number of revolutions experienced by the roller, and being constructed of steel, can wear out the guide track or well.
U.S. Pat. No. 4,374,496 describes roller assemblies incorporating parallel axis sets of guide and pusher rollers mounted above and below each other, to obviate the wide tire problem. This design leads to other problems, and does not completely solve the problem of eliminating drag of the guide rollers. Specifically, the high profile of this design, while purportedly improving the mechanical advantage, can cause tangling with tire washing mechanisms. If smaller diameter rollers are used to lower the profile, the smaller diameter of the rollers causes an excessive number of revolutions and early wearout.
In this design, as the roller assembly tilts under load, both roller sets approach tangency with the tire periphery, and again results in the tire engaging both sets of rollers, causing dragging of the guide rollers and their early failure.
The high profile of the stacked set of rollers creates a high center of gravity and greater resistance to being pulled through a trap door covering the point of entrance, Also, the guide rollers lead the pusher rollers so that the center of gravity is somewhat forward, even though the roller arm is tilted rearwardly. These factors combine to increase the tendency of the rollers to catapult as the roller moves through the entrance door, flipping to a tilted forward position rather than a tilted back, normal position.
In the tilted forward position, the lowered profile of the roller sometimes causes submarining of the rollers under the tire or lurching of the vehicle as the rollers flip back, both undersirable occurrences.
Other similar problems have been encountered with this design, i.e., tire contact with the roller support member, and dragging of the chain on the rollers during the return leg of the chain travel, as well as end wear on the rollers if the chain is pulling to either side.
In the design shown in U.S. Pat. Re. No. 30,026, the on-demand engagement feature is provided by a pivoting ramp which guides the rollers upward from a non-engaging level beneath the track through the trap door cover.
The ramps are pivoted by a power cylinder running parallel to the ramp and require a linkage system to pivot the ramps, which linkage system develops looseness, again leading to early failure. Misalignment and jamming of the rollers at the entrance door can also result from the ramps being improperly located.
Accordingly, it is an object of the present invention to provide an auto conveyor of the type described in which contact of a vehicle tire with the guide rollers is reliably prevented, and at the same time the roller assembly is of low profile to minimize the possibility of entanglement with tire washers.
Another object of the present invention is to provide an auto conveyor having a roller assembly which is not subject to early wear out, runs smoothly, and eliminates the tendency to catapult and reverse the rollers.
It is yet another object to provide an auto conveyor of the type described in which the pivoting of the ramp arms is actuated by a simple and reliable mechanism which minimizes the development of looseness and misalignments.